The present invention relates to a spinner disc for a rotary fiberization process and a rotary fiberization process which utilizes the spinner disc, and, in particular, to a spinner disc which has a plurality of slits in an inner annular portion of the spinner disc base plate that pass completely through the base plate from an upper surface of the base plate to a lower surface of the base plate and radiate outward from a periphery of a central bore in the spinner disc base plate. These; slits relieve stresses in the base plate and permit hot gases to pass out from within the spinner disc during operation which can further heat the underside of the spinner disc and a region adjacent an outer corner of the spinner disc to maintain a lower portion of a spinner disc sidewall adjacent.the outer annular comer of the spinner disc at a higher temperature for improved fiberization.
In high temperature rotary fiberization processes which fiberize molten thermoplastic fiberizable materials by using centrifugal force to pass the molten thermoplastic fiberizable material through rows of fiberizing holes in an annular peripheral sidewall of a spinner disc, such as but not limited to rotary glass-fiberizing processes which typically fiberize molten glass at temperatures in excess of 1800xc2x0 F., the base plate of the spinner discs undergoes high initial transient stresses during the start-up of the fiberizing operation. These high initial transient stresses can be above the yield strength of the high temperature resistant alloy used to form the spinner disc and can cause elastic-plastic fracture of the base plate and spinner disc failure.
The base plate of a spinner disc has a central bore therein on a rotational axis of the spinner disc for mounting the spinner disc on a drive shaft; an outer annular portion for receiving the hot molten thermoplastic fiberizable material to be fiberized; and an inner annular portion intermediate the central bore and the outer annular base plate portion. The spinner disc is normally preheated during the start-up of such high temperature fiberizing operations to reduce the stresses in the spinner disc at the start-up of a fiberzing operation. However, during start-up when the hot molten thermoplastic fiberzable material, e.g. glass at a temperature in excess of 1800xc2x0 F., is first introduced onto the outer annular portion of the spinner disc base plate, the temperature differential between the outer annular portion of the base plate and the inner annular portion of the base plate, adjacent the central bore, can be in excess of 800xc2x0 F. or 900xc2x0 F. with the temperature of the outer annular portion of the base plate about 1400xc2x0 F. and the temperature of the inner annular portion of the base plate, adjacent the central bore, about 500xc2x0 F. This transient temperature differential at start-up sets up transient compressive stresses in the outer annular portion of the base plate and transient tensile stresses in the inner annular portion of the base plate which can cause the base plate of the spinner disc to rupture, come apart or fail and, thus, the spinner disc, which is typically rotating at thousands of revolutions per minute, to fail at the start-up of the fiberizing operation. The potential for such failures presents both operational and safety problems in a commercial production line.
For good fiberization of molten thermoplastic fiberizable materials in high temperature rotary fiberization processes that use centrifugal force to pass the molten thermoplastic fiberizable material through rows of fiberizing holes in an annular peripheral sidewall of a spinner disc, such as but not limited to rotary glass fiberizing processes which typically fiberize molten glass at temperatures in excess of 1800xc2x0 F., the temperature of the annular peripheral sidewall must be maintained high enough for proper glass flow through the fiberizing holes in the annular peripheral sidewall. Thus, for good fiberization sufficient heat must be delivered to the annular sidewall of the spinner disc and retained in the annular sidewall to maintain the sidewall at the temperature desired for fiberization. In practice, the lower portion of the spinner disc sidewall adjacent the juncture of the spinner disc base plate and the spinner disc sidewall, where the lower rows of fiberizing holes are located, has been difficult to maintain at a desired temperature for good fiberization. For example, it is possible for this outer annular corner of the spinner disc and the lower rows of fiberizing holes adjacent this outer annular comer to become too cold for proper fiberization due to the entrapment of ambient air, fluid turbulence, and fluid recirculation in the region of the outer annular comer of the spinner disc. One relatively expensive and cumbersome method used to retain heat in the base plate and the lower portion of the spinner disc sidewall, adjacent the outer annular comer of the spinner disc, to keep this portion of the sidewall at a higher temperature for good fiberization involves securing an insulator plate or disc to the underside of the spinner disc. The insulator plate or disc is spaced below the underside of the spinner disc, is generally coextensive in size with the underside of the spinner disc, and both insulates and radiates heat back onto the underside of the spinner disc to maintain the underside of the spinner disc and the lower portion of the spinner disc sidewall adjacent the outer comer of the spinner disc at a higher temperature for good fiberization. However, this solution to the problem requires the use of additional components and the cost of the insulator plate and its installation and maintenance add to the production costs of the manufacturing operation.
The present invention provides a cost effective solution to both of the problems discussed above which have plagued high temperature rotary fiberization processes i.e. the high transient stresses normally encountered in the spinner disc base plates at start-up and the need to maintain the lower portions of the spinner disc sidewalls at a sufficiently high temperature for good fiberization. The spinner disc of the present invention includes: a base plate and an annular peripheral sidewall extending upward from and integral with the base plate which has a plurality of rows of fiberizing holes therein for fiberizing thermoplastic fiberizable materials by centrifugal force. The base plate has: a central bore therein on a rotational axis of the spinner disc for mounting the spinner disc on a drive shaft; an outer annular portion for receiving molten thermoplastic fiberizable materials to be fiberized; and an inner annular portion intermediate the central bore and the outer annular base plate portion. The base plate has a plurality of slits in the inner annular portion passing completely through the base plate from an upper surface of the base plate to a lower surface of the base plate and radiating outward from a periphery of the central bore. These slits relieve stresses in the base plate and permit hot gases to pass out from within the spinner disc during operation to heat the underside of the base plate and the region adjacent the outer lower corner of the spinner disc where the base plate meets the sidewall to help maintain the lower portion of the spinner disc sidewall and the fiberizing holes in the lower portion of the spinner disc sidewall at a desired temperature for fiberization.